Apparatus for processing workpiece with sandblasting

ABSTRACT

There is disclosed a method of and an apparatus for performing, using a sandblasting, a processing such as a chamfering of a workpiece which has a surface to be processed and a surface not to be processed located adjacent to each other. The workpiece (W) held by a holder (2) on a turntable (1) is transferred to a processing station (P 1 ) by the rotation of the turntable (1). An injection nozzle (3) or (4) is directed toward the surface to be processed (f 1 ) of the workpiece (W), while a jet nozzle (5) is directed toward the surface not to be processed (f 2 ). The jet nozzle (5) is supplied with fluid such as air, and the nozzle (3) or (4) is supplied with air containing abrasive grains. The fluid discharged from the jet nozzle (5) prevents the abrasive grains from impinging against the surface not to be processed (f 2 ).

FIELD OF THE INVENTION

This invention relates to a processing method of and its apparatus forprocessing, utilizing a sandblasting, a workpiece which has a surfacenot to be processed adjacent a surface to be processed.

BACKGROUND ART

A chamfering of an end edge Wa of a relatively small workpiece W, suchas one shown in FIG. 1, and a peripheral edge Wc of a bore Wb therein,has conventionally been performed by a hand process, utilizing athread-like abrasive tape. However, such method has disadvantages inthat it is troublesome, time-consuming and inefficient.

As an automated method of such a processing, a processing methodutilizing a sandblasting is proposed in which abrasive grains comprisedof, for example, silica sand, chilled cast iron or the like are causedto strongly impinge against a workpiece surface to be processed.However, as in the case of a head for a video signal recording andreproducing apparatus, for example, in which the workpiece W has a f₂requiring a mirror finish adjacent surfaces f₁ to be processed by thesandblasting, there would be a fear that the abrasive grains of thesandblasting impinge also against the surface f₂ to exert a badinfluence thereupon. For this reason, as matters stand, theconventionally general technology does not allow the sandblasting to beadopted for processing of the workpiece W.

Accordingly, an object of the present invention is to provide aprocessing method which can process, utilizing a sandblasting, aworkpiece which has a surface not to be processed adjacent a surface tobe processed.

Another object of the present invention is to provide an apparatusutilizing such processing method.

SUMMARY OF THE INVENTION

According to this invention, there is provided a method of processing aworkpiece wherein, while blowing fluid against a first portion of theworkpiece, abrasive grains are caused to impinge against a secondportion of the workpiece, to process only the second portion by theabrasive grains while preventing the abrasive grains from impingingagainst the first portion by the fluid.

In addition, according to this invention, there is provided a processingapparatus comprising abrasive grain supply means for supplyingpressurized fluid containing abrasive grains, fluid supply means forsupplying pressurized fluid, a first nozzle for blowing the pressurizedfluid against a first portion of a workpiece, and a second nozzle forflowing the pressurized fluid containing the abrasive grains against asecond portion of the workpiece.

Furthermore, according to this invention, there is provided a processingapparatus further comprising a vacuum generating means and a suctionport connected to the vacuum generating means and opening adjacent thefirst and second nozzles, so that the injected abrasive grains aredrawn.

Moreover, according to this invention, there is provided a processingapparatus characterized in that a collecting means is provided betweenthe suction port and the vacuum generating means for collecting thedrawn abrasive grains.

Furthermore, according to this invention, there is provided a processingapparatus wherein the abrasive grains collected by the collecting meansare supplied to the abrasive grain supply means so that the abrasivegrains are recirculated.

Furthermore, according to this invention, there is provided a processingapparatus wherein a bypass passage capable of being opened and closed isprovided between a first abrasive grain path disposed between theabrasive grain supply means and the second nozzle, and a second abrasivegrain path disposed between the suction port and the vacuum generatingmeans.

In addition, according to this invention, there is provided a processingapparatus wherein a first valve disposed at a side of the first abrasivegrain path downstream of the bypass passage, a second valve for openingand closing the bypass passage, and control means for controlling theopening and closing of the first and second valve are provided, thecontrol means opening the first valve and closing the second valve whenthe workpiece is processed, and in the case other than this, closing thefirst valve and opening the second valve.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing an example of a workpiece;

FIG. 2 is a schematic view showing an arrangement of a processingapparatus in accordance with this invention;

FIG. 3 is a side elevational view of a portion of the apparatus of FIG.2, illustrating a positional relationship between a rotary table 1 and ajet nozzle 5;

FIG. 4 is a perspective view showing a support structure for injectionnozzles 3 and 4 in the apparatus of FIG. 2;

FIG. 5 is a perspective view of the apparatus of FIG. 2; and

FIG. 6 is a cross-sectional view of an air blowing unit 27 in theapparatus of FIG. 2.

BEST MODE FOR CARRYING OUT THE INVENTION

FIGS. 2 and 3 show an example of a basic structure of a processingapparatus in accordance with the present invention. In FIGS. 2 and 3, Bis a base on which a rotary table 1 is disposed. An outer peripheralportion of the rotary table 1 is provided with four holders 2equidistantly spaced from each other wherein objects W (as a matter ofconvenience, the object shown in FIG. 1 is regarded as a workpiece) canbe respectively held by the holders 2 and be intermittently transferredone by one to a processing station P₁. In this case, the rotary table 1is driven by a motor 1a and is stopped by means of a limit switch or thelike not shown, when the table is rotated to a predetermined position.The above-described processing station P₁ has disposed thereat twoinjection nozzles 3 and 4 and a single jet nozzle 5. The injectionnozzles 3 and 4 are provided for strongly blasting abrasive grainsdelivered from a tank 7 through pipes 8 and 9 by compressed air providedby an operation of an air compressor 6, against the surface to beprocessed f₁ of the object W. Since, in case of the object W shown inFIG. 1, the surfaces to be processed f₁ are two in back to backrelation, the nozzles 3 and 4 are mounted on a slider 10, as shown inFIG. 4, in such a manner that tips of the respective nozzles face towardeach other. The arrangement is such that the nozzles 3 and 4 are axiallymoved by the movement of the slider 10 by a motor 11 in such a mannerthat when one of the injection nozzles 3 moves perpendicularly towardone of the surfaces to be processed f₁ of the object W at the processingstation P₁, the other injection nozzle 4 moves away from the othersurface to be processed f₁, and, when the injection nozzle 4 movestoward the surface to be processed f₁ facing thereto, the otherinjection nozzle 3 moves away from the other surface to be processed f₁.

As shown in FIG. 4, the slider 10 is supported by the base B, forexample, through a supporting member A.

The jet nozzle 5 is provided for strongly blowing exclusion fluid suchas air for excluding the abrasive grains, against the surface not to beprocessed f₂ of the object W. Since the surface not to be processed f₂is formed by an upper surface of the object W, the nozzle 5 is disposedabove the rotary table 1, as shown in FIG. 2, so as to extendperpendicularly to the surface not to be processed f₂ of the object W atthe processing station P₁, and the nozzle 5 is connected to a supplysource 31 of the exclusion fluid through a pipe 13 and a valve 30.

In addition to the two nozzles 3 and 4, the slider 10 has thereon asuction unit 14 which is in communication with a dust collection device16 through a pipe 15. The dust collecting device 16 draws the abrasivegrains having processed the object W and dust generated upon theprocessing, through the suction unit 14, to separate the abrasive grainsfrom the dust, to thereby purify the air which is discharged to theatmosphere by a blower 17. The dust collecting device 16 is connected tothe tank 7 through a communication duct 19 having provided therein adamper 18 so as to be able to return the recovered abrasive grains tothe tank 7. The above-described pipes 8, 9 and 15 have respectivelyprovided therein valves 20, 21 and 22, and the pipe 8 and the pipe 15are connected to each other by a bypass tube 24 having provided thereina valve 23, at the side of the above-described valve 20 adjacent thetank 7 and at the side of the valve 22 adjacent the dust collectingdevice 16. Accordingly, with this arrangement, the abrasive grains areinjected from the two injection nozzles 3 and 4 by the simultaneousopening of the valve 20 and the two valves 21 and 29, the abrasivegrains are injected against the surface to be processed f₁ from any oneof the injection nozzles 3 and 4 by the opening of only one of the twovalves 21 and 29 to enable the processing, and during the interruptionof the processing, the closing of the valve 20 and the opening of thevalve 23 allow the abrasive grains to be recirculated in the order ofthe tank 7--pipe 8--bypass tube 24--pipe 15--dust collecting device16--communication duct 19--tank 7, to maintain the abrasive grains in afluent condition, so that it is possible to stably supply the abrasivegrains to the injection nozzles 3 and 4, rapidly simultaneously with thestart of the processing.

A stop station P₂ subsequent to the processing station P₁ of theabove-described rotary table 1 has arranged thereat blowing nozzles 25and 25 for blowing clean air against the object W having the processingcompleted, to remove, from the object W, dust such as the abrasivegrains adhering thereto. The blowing nozzles 25 and 25, the injectionnozzles 3 and 4, the jet nozzle 5 and the suction unit 14 are covered bya cover 26, as shown in FIG. 5, which cooperates with an approximatehalf of the rotary table 1 to form a single, large processing chamber,so that the dust generated by these components is prevented fromscattering to the outside, but is drawn into the dust collecting device16. As shown in FIGS. 5 and 6, an air blowing unit 27 is provided, at afeeding-in side of the cover 26 at which the object W having not yetbeen processed is fed thereinto, for forming an air-curtain at thefeeding-in side, and brushes 28 are provided at a feeding-out sidethereof for the object W having been processed, so that the object W isfreely capable of being fed in and out of the interior of the cover 26,and the interior and exterior of the cover 26 are shielded from eachother.

In the above-described arrangement, the motors 1a and 11, valves 20 to23, 29 and 30 are controlled by a controller 40.

A processing method of the object by means of the sandblasting carriedout by the above-described processing apparatus will now be described.

The object W which is a subject of the processing is loaded on theholder 2 at a station P of the rotary table 1, and is transferred to theprocessing station P₁ by the intermittent rotation of the rotarytable 1. As one object W stops at the processing station P₁, the motor11 is actuated to first cause the injection nozzle 3 to move toward oneof the surfaces to be processed f₁. As the injection nozzle 3 reaches apredetermined injection position, the air is discharged from the jetnozzle 5 toward the surface not to be processed f₂ of the object W,simultaneously therewith, the valves 20 and 21 associated with theinjection nozzle 3 are opened, the valve 23 in the bypass tube 24 isclosed, and the abrasive grains recirculated through a passage comprisedof the tank 7, pipe 8, bypass tube 23, pipe 15, dust collecting device16 and communication duct 19 are injected from the injection nozzle 3toward the surface to be processed f₁ through the pipe 9 to process thesurface. That is, the flash removal and the chamfering take place on theedges Wa and Wc at the side of the surface to be processed f₁. In thiscase, the air from the jet nozzle 5 is injected at a velocity (pressure)higher than that of the abrasive grains, so that after the impingementof the air against the surface not to be processed f₂, the air flowsalong the surface not to be processed f₂, to prevent the abrasive grainsinjected from the injection nozzle 3 from being brought into contactwith the surface not to be processed f₂.

When the processing of one of the surfaces to be processed f₁ has beencompleted in this manner, the valve 21 is closed and the valve 23 isopened so that the abrasive grains are recirculated as described above,and the motor 11 is actuated to move the injection nozzle 3 away fromthe surface to be processed f₁ on which the processing has beencompleted, and to move the other injection nozzle 4 toward the surfaceto be processed f₁ which has not yet been processed. As this has beencompleted, the valve 29 associated with the injection nozzle 4 isopened, and the valve 23 is closed, so that the abrasive grains areinjected from the injection nozzle 4 to process the surface to beprocessed f₁ which has not yet been processed. As the processing of thetwo surfaces to be processed f₁ of one object W has been completed, therotary table 1 is rotated so that a new object W attached at the stationP is transferred to the processing station P1, and the object W on whichthe processing has been completed is transferred to the subsequentstation P₂. At the station P₂, the blowing nozzles 25 and 25 areactuated to blow the air against the processed object W to clean thesame, and in this case, all of the air and the abrasive grainsdischarged within the cover 26 until now, together with the dust arecollected into the dust collecting device 16 through the suction unit14. The abrasive grains thus drawn into the dust collecting device 16are separated from the dust and are returned to the tank 7 through thecommunication duct 19 for re-use in the processing.

The processed object W from which the dust and abrasive grains areremoved at the station P₂ and which is fed out of the cover 26 isremoved from the holder 2 at a station P₃.

The illustrated processing apparatus utilized for the description of thepresent invention is merely an example, and does not limit theprocessing method of the present invention.

Reference items when the present invention is carried out will beenumerated below.

(1) The jet nozzle 5 is normally disposed such that the exclusion fluidimpinges against the surface not to be processed f₂ perpendicularlythereto, but it is possible to cause the exclusion fluid to obliquelyimpinge against the surface not to be processed f₂ to exclude theabrasive grains.

(2) The abrasive grain exclusion performance of the exclusion fluidjetted from the jet nozzle 5 has intimate relation to the velocity,specific gravity, particle size and the like of the abrasive grainsinjected from the injection nozzles 3 and 4.

(3) Although air is mainly utilized as the exclusion fluid jetted fromthe jet nozzle 5, it is possible to utilize liquid such as water.

As described above, in the present invention, since the abrasive grainsare caused to impinge against the surface to be processed locatedadjacent the surface not to be processed, while the exclusion fluid isblown against the surface not to be processed, to avoid the impingementof the abrasive grains against the surface which has not to beprocessed, by the exclusion fluid to perform the processing, it ispossible to process only the surface to be processed by thesandblasting, without damage due to the abrasive grains on the surfacewhich has not to be processed. In addition, since it is sufficient onlyto provide a jetting system of the exclusion fluid which is similar influid jetting function to the sandblasting, there is also provided anadvantage that the processing apparatus is simple in structure.

Industrial Applicability

This invention is very useful for use in a processing where a chamferingtakes place on a relatively small workpiece having a surface to beprocessed and a surface not to be processed which are located adjacentto each other, as is the case with a head for a video tape recorder, forexample.

What is claimed is:
 1. An apparatus for sandblasting a workpiece havinga first portion not to be processed and a second portion to beprocessed, comprising:(a) holding means for holding said workpiece insaid prescribed processing station; (b) fluid blowing means for blowinga pressurized fluid against said workpiece, said fluid blowing meansincluding at least one nozzle disposed in said processing station fordirecting the pressurized fluid to said first portion of said workpiece;(c) abrasive grain blowing means for causing abrasive grains to impingeagainst said workpiece to thereby sandblast said workpiece, saidabrasive grain blowing means including abrasive grain supply means forsupplying the abrasive grains carried on a carrying fluid, at leastanother nozzle disposed in said processing station, a first abrasivegrain path means connecting said at least another nozzle with saidabrasive grain supply means for directing the abrasive grains suppliedfrom said abrasive grain supply means to said second portion of saidworkpiece, and a first valve mounted on said first abrasive grain pathmeans for opening and closing said first abrasive grain path means foropening and closing said first abrasive grain path means; (d) suctionmeans for collecting the abrasive grains blown against said workpiece,said suction means comprising vacuum generating means, a suction portdisposed in said processing station, a second abrasive grain path meansconnecting said suction port to said vacuum generating means for drawingsaid blown abrasive grains thereinto, and collecting means disposedbetween said suction port and said vacuum generating means forcollecting said drawn abrasive grains to recirculate the abrasive grainsinto said abrasive grain supply means; (e) fluidizing means for keepingsaid abrasive grains flowing when the processing of the workpiece isinterrupted, said fluidizing means comprising a bypass passageconnecting and second abrasive grain path to a portion of said firstabrasive grain path located upstream from said first valve and a secondvalve mounted on said bypass passage; and (f) control means foroperating said abrasive grain blowing means and said fluid blowing meansconcurrently, to thereby prevent the abrasive grains from impingingagainst said first portion and to cause the abrasive grains to impingeagainst only said second portion of said workpiece, said control meansbeing operable to open said first valve and close said second valve whenthe workpiece is processed and to close said first valve and open saidsecond valve to thereby cause said abrasive grains to be circulatedthrough said bypass passage when the workpiece is not processed.
 2. Aprocessing apparatus according to claim 1, in which said workpiece has apair of the second portions spaced from each other, said abrasive grainblowing means comprising a slider disposed in said processing stationfor sliding movement along said workpiece and a pair of said anothernozzles mounted on said slider and spaced from each other in a directionof sliding movement of said slider, said control means being operable toselectively move said slider between a first position wherein one of thesecond nozzles is directed to one of the second portions of theworkpiece and a second position wherein the other of said pair of saidanother nozzles is directed to the other second portion of theworkpiece.
 3. A processing apparatus according to claim 2, in which saidsuction port is mounted on said slider.
 4. A processing apparatusaccording to claim 1, in which said fluidizing means further includes athird valve mounted on a portion of said second abrasive grain pathmeans located upstream from said bypass passage, said control meansbeing operable to open said third value when the workpiece is processedand close said third valve when the processing is interrupted.
 5. Aprocessing apparatus according to claim 1, in which said holding meanscomprises a rotary circular table, a plurality of holders disposed onsaid rotary table in circumferentially equally spaced relation to oneanother for holding the workpieces, respectively, and drive meansattahced to said rotary table for intermittently rotating said rotarytable to thereby index one of the workpiece in said processing stationto a clearing station which is spaced from said processing stationcircumferentially on said rotary table in a direction of rotation of therotary table.
 6. A processing apparatus according to claim 5, furthercomprising air blowing means disposed in said cleaning station forblowing air against said workpiece in said cleaning station to clean theworkpiece.
 7. A processing apparatus according to claim 6, furthercomprising a base on which said rotary table is mounted, and a coverdisposed on said base so as to surround said processing and cleaningstations to prevent dust produced at the stations from scattering to theoutside environment.
 8. A processing apparatus according to claim 7,further comprising an air blowing unit provided at a feeding-in side ofsaid cover through which the workpiece is fed into an interior of thecover, and brushing means provided at a feeding-out side of said coverfor preventing dust adhering to the workpiece from escaping outside ofthe cover.